Its not too complicated. First, find a pin or really anything that will fit in the hole. Try to find one that fits just right. Then, take a hammer and hit it really hard, multiple times. If the pin fits right you don't hace to worry aobut damaging it because you won't.

I'm going to do the first trigger job and I was thinking, I don't have a tap thingy so if I use my 11/64 bit and drill the hole in front of the trigger spring. and just screw the screw in hard, will it work? I figure it should if I'm careful but was wondering if anybody has done this and if the frames is hard to screw a hole in. Thanks.